Audio Questions, Im a dumbass and need some explaining Options

[Serhey]

so this isnt necessaraly for now, but i was thinking after i get my interior redone i wanna work on the audio system in my car. and well i know absolutely nothing about that stuff. i mean like what brands are good and what should i look for? what are the sizes and if i buy the right size can i just replace them, im hoping to do this all by myself. i dont think its that difficult its just im so foreign to it that i dont really know what to do and dont want to get ripped off if i try to buy the stuff at a store. i dont want to spend too much but i want a pretty good sounding system. what can i do to get good bass? i dont want to put in subs in my trunk. thanks.

[CelicaST_CALI]

Yea sorry i forgot to add that,crutchfield has SOME good deals,but they are usually overpriced so id use it just to get info on a piece of equipment then buy somewhere cheaper